1. Field of the Invention
The present invention relates to thin electrically conductive films, and more specifically, the present invention relates to a wet-bench method for producing substantially pure electrically conductive films.
2. Background of the Invention
In microelectronics, device performance is strongly related to the microstructure and the electrical resistivity of thin film electrodes.
During the last two decades, strontium ruthenium oxide (SRO) thin film electrodes have received considerable attention because of their high metallic conductivity and high temperature stability (1200 K or 927° C.) in oxidizing or inert atmospheres, making them suitable in numerous technological applications. Moreover, SRO films improve the fatigue and imprint behavior of ferroelectric materials such as barium strontium titanate (BST) and lead lanthanum zirconate titanate (PLZT), due to minimal lattice mismatch between the film and the ferroelectric materials.
Considering various applications of SRO films, extensive efforts have been devoted to depositing device-quality SRO thin films on (100)Si, (100)SrTiO3, (100)LaAl03, and (100)MgO substrates. These efforts rely on expensive and complicated techniques like RF sputtering, pulsed laser deposition (PLD), dc magnetron sputtering, and metal-organic chemical vapor deposition (MOCVD).
Researchers have used metal-organic decomposition to form SRO powders and films on silicon substrates with different precursors. However, these powders and films included unidentified impurities (secondary phases) and RuO2. Moreover, the fabricated SRO films on silicon substrates are randomly oriented such that the lattice formed by the cations in the films is not aligned with the lattice defining the underlying substrate.
Processes of depositing SRO films on steel substrates are sensitive to pyrolysis and crystallization temperatures. For example, precursor ruthenium nitrosyl nitrate decomposes to unwanted RuO2 phase at temperatures as low as 260° C. And at such low pyrolysis temperatures, not all organics are removed, therefore leading to inhibition of the formation of the metal-oxygen-metal (M-O-M) gel network. Additionally, the undesired RuO2 phase does not change during the final crystallization anneal even at higher temperatures.
Strontium metal and strontium chloride precursors have been used to fabricate SRO films with resistivity of 1100-20000/μΩ-cm. However, chlorine containing precursor compounds are typically detrimental to the electrical properties due to incomplete removal of chlorine after crystallization and the diffusion of residual chlorine into the dielectric layers that are subsequently deposited.
A need exists in the art for a wet-bench process for producing strontium ruthenium oxide films. The process should yield substantially pure phase SRO films. The process should also provide films with electrical resistivities at least as low as 850±50 μΩ/cm for polycrystalline films and at least 300-400 μΩ/cm for oriented films.